MANSEHRA, Pakistan (AP) — A bus carrying about two dozen wedding guests fell into the Indus River in northern Pakistan on Tuesday, killing at least 18 people, officials said.

It happened in the Gilgit Baltistan region as the bus was heading to Chakwal, a city in Punjab province, government spokesman Faizullah Farqan said.

He said a search for bodies continued, and so far only one woman had been found alive and was being treated at a hospital.

Police said it was unclear what caused the crash, and officers were yet to record the lone survivor's statement.

Pakistani President Asif Ali Zardari offered condolences and asked rescuers to expedite efforts to find missing passengers.

Road accidents are common in Pakistan due to poor infrastructure and disregard for traffic laws and safety standards. In August, 36 people were killed and dozens of others were injured in two separate bus crashes.